<ol>
<li><p>There are many prep books out there. ie. Barron’s, Princeton Review, Kaplan, College Board, etc. You should consider taking an SAT II for a class that you are taking or have taken in school.</p></li>
<li><p>The vast majority of them are multiple choice, with the same grading/penalty system as the SAT I. The number of questions varies from test to test. They test your knowledge of a particular subject.</p></li>
<li><p>Same grading system.</p></li>
<li><p>Different tests have different curves. As for the difficulty, try some practice tests and determine how hard they are for you.</p></li>
</ol>